3.1L Woes...
Radiohobbyist
10-24-2006, 12:02 AM
Hello, everyone, first post. :grinyes:
I've a 1994 Achieva SC, with 3.1L [code M] and automatic, and >155,000 miles [>248 000 Km] on her.
Two problems that I'm having at the moment, I'm wondering if are caused by the same malfuncting part. These occur after the engine has reached operating temperature [and I assume that the ECM has gone into closed-loop mode].
The first is that after a prolonged cruise [either manually or with Cruise Control], upon deceleration the Service Engine light comes on. The engine behaves normally, and after being shut off for at least ten seconds and restarted, the light does not come back on. This makes me think that it's an intermittent problem.
The second is that while "creeping" [say, in a parking lot, at idle], the engine "surges." It seems that it wants to die but then "gooses" itself; although it does die sometimes. It restarts normally, and any throttle above idle is fine.
I've replaced the MAP and Throttle Position sensors, to no avail. Although, the TPS was a little worn mechanically, so that purchase might not have been in vain.
I'm thinking that this might have something to do with the Idle-Air Control valve, but wanted to run this past those here who may have had similar trouble. I've been told to plug the car into a diagnostic scanner, but can't find an auto-part store with anything other than an OBD-II unit to borrow/rent. And of course, mine is one of the last OBD-I systems where GM changed the firmware and the ALDL connector under the dash.
*Sigh* Any ideas? Thanks! :)
I've a 1994 Achieva SC, with 3.1L [code M] and automatic, and >155,000 miles [>248 000 Km] on her.
Two problems that I'm having at the moment, I'm wondering if are caused by the same malfuncting part. These occur after the engine has reached operating temperature [and I assume that the ECM has gone into closed-loop mode].
The first is that after a prolonged cruise [either manually or with Cruise Control], upon deceleration the Service Engine light comes on. The engine behaves normally, and after being shut off for at least ten seconds and restarted, the light does not come back on. This makes me think that it's an intermittent problem.
The second is that while "creeping" [say, in a parking lot, at idle], the engine "surges." It seems that it wants to die but then "gooses" itself; although it does die sometimes. It restarts normally, and any throttle above idle is fine.
I've replaced the MAP and Throttle Position sensors, to no avail. Although, the TPS was a little worn mechanically, so that purchase might not have been in vain.
I'm thinking that this might have something to do with the Idle-Air Control valve, but wanted to run this past those here who may have had similar trouble. I've been told to plug the car into a diagnostic scanner, but can't find an auto-part store with anything other than an OBD-II unit to borrow/rent. And of course, mine is one of the last OBD-I systems where GM changed the firmware and the ALDL connector under the dash.
*Sigh* Any ideas? Thanks! :)
BNaylor
10-24-2006, 10:12 AM
Welcome to AF.
If you suspect the IAC the best thing to do is remove it and clean the spring loaded pintle and the seat at the throttle body (TB) with carb or throttle body spray cleaner. Also, clean the TB bore. The TB and IAC are susceptible to carbon buildup and the air passages/orifice may get blocked.
If you suspect the IAC the best thing to do is remove it and clean the spring loaded pintle and the seat at the throttle body (TB) with carb or throttle body spray cleaner. Also, clean the TB bore. The TB and IAC are susceptible to carbon buildup and the air passages/orifice may get blocked.
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